1. Field of the Invention
The present invention relates to a crystal oscillator having a plurality of output blocks for implementing multiple output. More particularly, the crystal oscillator using an Integrated Circuit (IC) chip comprises an additional output terminal on the underside thereof, in which an additional IC chip having an output-adjusting block connected to the additional output terminal is mounted on the crystal oscillator or an output-adjusting block added to the IC chip is connected to the additional output terminal.
2. Description of the Related Art
As well known in the art, crystal oscillator circuits using crystal have a number of advantages in actual application since crystals show high frequency stability and stable temperature characteristic as well as excellent processability. These advantages result in a current popularity of crystal oscillators each of which is constructed into a single package by incorporating a crystal into an oscillator circuit and which are capable of generating a preferred clock frequency by applying rated voltage only. In the telecommunication field, a crystal oscillator necessarily has an adjustable frequency in a specific range in order to maintain synchronization among a number of signals or to synchronize a system clock with a transmitting carrier wave. In order to synchronize the oscillation frequency of the crystal oscillator, an adjustable-capacitance device is generally used as a load capacitor in respect to the crystal. The adjustable-capacitance device adopts, for example, a varicap with a capacitance which is adjustable according to applied DC voltage. The crystal oscillator having the above functions is referred to as Voltage Controlled Crystall Oscillator (VCXO). An example of the VCXO is disclosed in U.S. Pat. No. 4,302,731.
As shown in FIG. 1, a crystal oscillator adjusts the frequency of a signal with an Automatic Frequency Controlling (AFC) block and a frequency-adjusting block and resonates the frequency into a specific frequency with a crystal resonator. The crystal oscillator further comprises an oscillating block for oscillating the frequency resonated by the crystal resonator and a component for outputting the oscillated frequency.
A crystal oscillator having a temperature-compensating circuit is also widely used to provide a uniform reference frequency regardless of surrounding temperature variation. This type of crystal oscillator is referred to as Temperature Compensated Crystal Oscillator (TCXO), an example of which is shown in U.S. Pat. No. 4,951,007. A Voltage Controlled Temperature Compensated Crystal Oscillator (VC-TCXO) is frequently used, in which a voltage controlling function is added for more precise frequency adjustment. Such a TCXO, as shown in FIG. 2, additionally comprises a temperature-compensating block in the structure of FIG. 1.
In using frequency signals outputted from the above crystal oscillators, the frequency signals are used as they are. Alternatively they may be amplified or converted into desired signals. As set products related to mobile communication such as mobile phones are recently diversified in their functions, each set product requires a signal having a waveform different from that of the original signal oscillated from the crystal oscillator, e.g. a signal of high amplitude. For the purpose of obtaining the high amplitude signal, a set product is mounted with a crystal oscillator and then, separately, a component for amplifying the amplitude of the original signal from the crystal oscillator. The above added component occupies a certain space in the set product, resultantly creating drawbacks that downsizing of the set product is obstructed while the design thereof is complicated. In this regard, incorporating a portion of a circuit set using a crystal oscillator into the crystal oscillator may further downsize the set product.
According to the structures of typical crystal oscillators of the prior art, however, the component on the set product cannot be incorporated therein. In a conventional crystal oscillator 100, as shown in FIG. 3, a chip 105 is mounted in a cavity provided above a substrate 103, and then a crystal oscillator unit 109 having the same size as that of the substrate 103 is mounted on the substrate 103 and connected electrically through terminal pads 107. A crystal resonator is usually contained inside the crystal oscillator unit 109. The oscillator is further provided with a voltage controlling terminal 111, a ground terminal 112, and output terminal 113 and an input terminal 114 on the underside of the substrate 103. Such an oscillator structure has a single output terminal, and the outputted signal from the single output terminal is to be adjusted through additional component on the set product (not shown) to produce amplified signal.
It is accordingly required to develop a crystal oscillator with a multiple output function wherein a component on a set product for amplifying the output signal is incorporated or wherein the circuit for multiple output function is added to the conventional IC.
The present invention has been made to solve the above problems and it is therefore an object of the present invention to impart a multiple output function to a crystal oscillator by providing a conventional single output crystal oscillator with a circuit for enabling multiple output and a number of output terminals.
Further it is another object of the invention to provide a multiple output function so that necessary output can be selectively used as well as reduces external components on the set product, thereby to enable the downsizing and multiple functioning of the product.
According to an aspect of the invention, to accomplish the above objects, it is provided a multiple output crystal oscillator comprising a crystal resonator; a first IC chip having an oscillating circuit block for oscillating a resonance signal from the crystal resonator and a frequency-adjusting circuit block; a second IC chip having an output-adjusting block for adjusting the oscillation signal from said oscillating circuit block of the first IC chip into at least one different waveform and then outputting those adjusted signals; and a substrate structure for mounting the first and second IC chips and having output terminals on the underside, wherein the output terminals of the substrate include a basic output terminal for outputting the oscillation signal from the first IC chip and at least one additional output terminal for outputting at least one waveform-adjusted oscillation signal from the second IC chip.
According to another aspect of the invention to obtain the above objects, it is provided a multiple output crystal oscillator comprising: a crystal resonator; an IC chip having an oscillating circuit block for oscillating a resonance signal from the crystal resonator, a frequency-adjusting circuit block and an output-adjusting block for adjusting the oscillation signal from said oscillating circuit block into at least one different waveform and then outputting those adjusted signals; and a substrate structure for mounting the IC chip and having output terminals on the underside, wherein said output terminals of the substrate include a basic output terminal for outputting the oscillation signal from said oscillating circuit block and at least one additional output terminal for outputting at least one waveform-adjusted oscillation signal from said output-adjusting block.